Semiconductor memory device

ABSTRACT

A semiconductor memory device includes a sense amplifier, and the sense amplifier includes a bus, first and second latch circuits, and a third transistor. The first latch circuit includes a first transistor connected to the bus, and the second latch circuit includes a second transistor connected to the bus. When data is transmitted from the first latch circuit to the second latch circuit, a third transistor is switched on to precharge the bus by applying a first voltage that is lower than a power source voltage of the first and second latch circuits to a gate of the third transistor. Thereafter, second and third voltages that are lower than the power source voltage are applied to gates of first and second transistors, respectively.

CROSS-REFERENCE TO RELATED APPLICATION

This application is based upon and claims the benefit of priority fromJapanese Patent Application No. 2013-052396, filed Mar. 14, 2013, theentire contents of which are incorporated herein by reference.

FIELD

Embodiments described herein relate to a semiconductor memory device.

BACKGROUND

A NAND flash memory in which memory cells are arranged in threedimensions is known in the related art.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of a semiconductor memory device according toa first embodiment.

FIG. 2 is a circuit diagram of a memory cell array according to thefirst embodiment.

FIG. 3 is a block diagram of a sense amplifier module according to thefirst embodiment.

FIG. 4 is a block diagram of one region of the sense amplifier moduleaccording to the first embodiment.

FIG. 5 is a circuit diagram of a sense amplifier unit according to thefirst embodiment.

FIG. 6 is a circuit diagram of a latch circuit according to the firstembodiment.

FIG. 7 is a flowchart of a method of transmitting data according to thefirst embodiment.

FIG. 8 is a timing chart of various signals at the time of datatransmission according to the first embodiment.

FIG. 9 is a circuit diagram of the sense amplifier unit according to thefirst embodiment.

FIG. 10 is a circuit diagram of the sense amplifier unit according tothe first embodiment.

FIG. 11 is a flowchart of a method of transmitting data according to asecond embodiment.

FIG. 12 is a timing chart of various signals at the time of datatransmission according to the second embodiment.

FIG. 13 is a circuit diagram of a sense amplifier unit according to thesecond embodiment.

FIG. 14 is a graph showing electric potentials of LBUS, LPC, and LTL.

FIG. 15 is a circuit diagram of one region of the sense amplifiermodule.

FIG. 16 is a schematic diagram illustrating a detail of a minimumelectric potential of a bus.

FIG. 17 is a flow chart of a method of transmitting data according to athird embodiment.

FIG. 18 is a timing chart of various signals at the time of datatransmission according to the third embodiment.

FIG. 19 is a circuit diagram of a sense amplifier unit according to thethird embodiment.

FIG. 20 is a flowchart of a method of transmitting data according to afourth embodiment.

FIG. 21 is a timing chart of various signals at the time of datatransmission according to the fourth embodiment.

FIG. 22 is a flowchart of a method of transmitting data according to afifth embodiment.

FIG. 23 is a timing chart of various signals at the time of datatransmission according to the fifth embodiment.

FIG. 24 is a flowchart of a method of transmitting data according to afirst example of a sixth embodiment.

FIG. 25 is a timing chart of various signals at the time of transmittingdata according to the first example of the sixth embodiment.

FIG. 26 is a timing chart of various signals at the time of transmittingdata according to a second example of the sixth embodiment.

FIG. 27 is a timing chart of various signals at the time of transmittingdata according to a third example of the sixth embodiment.

FIG. 28 is a circuit diagram of a voltage generation circuit accordingto a seventh embodiment.

FIG. 29 is a circuit diagram illustrating data transmission betweenlatches.

FIG. 30 is a circuit diagram further illustrating data transmissionbetween the latches.

FIG. 31 is a circuit diagram of a memory cell array according tomodification examples of the first to the seventh embodiments.

DETAILED DESCRIPTION

A semiconductor memory device according to an embodiment includes amemory cell array having multiple memory cells that are stacked above asemiconductor substrate and a sense amplifier that can retain data readfrom or to be written to a memory cell. The sense amplifier includes abus that can transmit the data, a first latch circuit, a second latchcircuit, and a transistor that controls precharging of the bus. Thefirst latch circuit includes a first data retention unit, and a firsttransistor that connects the first data retention unit and the bus. Thesecond latch circuit includes a second data retention unit, and a secondtransistor that connects the second data retention unit and the bus.When the data is transmitted from the first latch circuit to the secondlatch circuit, the third transistor is switched on by applying a firstvoltage lower than a power source voltage of the first and second latchcircuits to a gate of the third transistor to precharge the bus to anelectric potential lower than the power supply voltage. Furthermore,after precharging the bus, second and third voltages that are lower thanthe power source voltage are applied to gates of the first and secondtransistors, respectively.

Embodiments are described below referring to the drawings. Like partsare given like reference numerals throughout the drawings and in thedescription.

1. First Embodiment

A semiconductor memory device according to a first embodiment isdescribed. A three-dimensional stacked type NAND flash memory in whichmemory cells are stacked above a semiconductor substrate is describedbelow as an example of a semiconductor memory device.

1.1 Configuration of Semiconductor Memory device

First, a configuration of the semiconductor memory device according tothe present embodiment is described.

1.1.1 Entire Configuration of Semiconductor Memory Device

FIG. 1 is a block diagram of the semiconductor memory device accordingto the present embodiment. A NAND flash memory 1, as illustrated,includes a memory cell array 10, a sense amplifier module 11, a columnselector 12, an input and output circuit 13 and a control circuit 14.

The memory cell array 10 includes multiple (for example, N units) blocksBLK (BLK0, BLK1, BLK2, . . . ), each of which is a set of nonvolatilememory cells. Data inside the same block BLK are removed in a lump. Eachof the blocks BLK includes multiple (for example, M units) memory groupsGP (GP0, GP1, GP2, . . . ), each of which is a set of NAND strings 15 inwhich the memory cells are connected in series. The number of blocksinside the memory cell array 10 and the number of memory groups insidethe block are arbitrary.

The sense amplifier module 11 senses/amplifies data that is read frommemory cell at the time of data reading. Furthermore, during writing ofdata, write data is transmitted to a memory cell. The sense amplifiermodule 11 has a set of multiple sense amplifier units, a latch circuit,a bus, and the like. These are described in detail below.

The column selector 12 selects a column direction (a bit line describedbelow) of memory cell array 10.

The input and output circuit 13 governs transmitting and receiving ofdata between a NAND flash memory 1 and an outside controller or a hostapparatus. Then, the input and output circuit 13 outputs the data, whichare sensed/amplified with the sense amplifier module 11, to the outsideat the time of data reading. Furthermore, the input and output circuit13 receives write data from the outside and transmits the write data tothe sense amplifier module 11, at the time of data writing.

The control circuit 14 controls operation of the entire NAND flashmemory 1.

1.1.2 Memory Cell Array 10

Next, a configuration of the memory cell array 10 is described indetail. FIG. 2 is a circuit diagram of the block BLK0. The other blocksBLK have the same configuration.

As illustrated, the block BLK0 includes multiple memory groups GP.Furthermore, each memory group GP includes multiple (in the presentexample, L units) NAND strings 15.

Each NAND string 15 includes, for example, eight memory cell transistorsMT (MT0-MT7), selection transistors ST1, ST2 and a back gate transistorBT. The memory cell transistor MT includes a stacked layer gateincluding a control gate and an electric charge accumulation layer andretains data in a non-volatile state. Moreover, the number of the memorycell transistors MT is not limited to eight and may be 16, 32, 64, 128,or so forth. The number is not given any limitation. The back gatetransistor BT, like the memory cell transistor MT, includes the stackedlayer gate including the control gate and the electric chargeaccumulation layer. However, the back gate transistor BT is not forretaining the data, but functions to control an electric current path atthe time of data writing and erasing. The memory cell transistor MT andthe back gate transistor BT are arranged between the selectiontransistors ST1 and ST2 in such a manner that their electric currentpaths are connected in series. Moreover, the back gate transistor BT isprovided between the memory cell transistors MT3 and MT4. The electriccurrent path of the memory cell transistor MT7 at one end of this serialconnection is connected to one end of the electric current path of theselection transistor ST1, and the electric current path of the memorycell transistor MT0 at the other end is connected to one end of theelectric current path of the selection transistor ST2.

Gates of the selection transistors ST1 of the memory groups GP0 toGP(M−1) are commonly connected to select gate lines SGS0 to SGS(M−1),respectively, and gates of the selection transistors ST2 are commonlyconnected to the select gate lines SGS0 to SGS(M−1), respectively. Incontrast, the control gates of the memory cell transistors MT0 to MT7inside the same block BLK0 are commonly connected to word lines WL0 toWL7, respectively, and the control gates of the back gate transistors BTare commonly connected to back gate lines BG (BG0 to BG(N−1),respectively, in blocks BLK0 to BLK(N−1)).

That is, the word lines WL0 to WL7 and the back gate lines BG arecommonly connected between the multiple memory groups GP inside the sameblock BKL0, and in contrast, the select gate lines SGD and SGS areindependently provided for each memory group GP inside the same blockBLK0.

Furthermore, among the NAND strings 15 that are arranged in the form ofa matrix inside the memory cell array 10, the other end of the electriccurrent path of the selection transistor ST1 of the NAND string 15 s inthe same column is commonly connected to the same bit line BL. That is,the bit line BL commonly connects the NAND string 15 among the multipleblocks BLK. Furthermore, the other end of the electric current path ofthe selection transistor ST2 is connected to a source line SL. Thesource line SL commonly connects the NAND string 15, for example, amongthe multiple memory groups GP.

The data inside the memory cell transistor MT in the same block BLK areerased as a whole unit. In contrast, data reading and data writing areperformed with respect to multiple memory cell transistors MT that arecommonly connected to any one of the word lines WL, in any one of thememory groups GP of any one of the blocks BLK. The unit of data readingand data writing is called a “page.”

In the memory cell array 10 with the configuration described above, thememory cell transistor MT, the selection transistors ST1 and ST2 and theback gate transistor BT are stacked, in three dimensions, on thesemiconductor substrate. As one example, one part of a peripheralcircuit, such as the sense amplifier module 11, is formed on thesemiconductor substrate, and the memory cell array 10 is formed abovethe peripheral circuit.

A configuration of the memory cell array 10 is disclosed, for example,in U.S. patent application Ser. No. 12/407,403, entitled “THREEDIMENSIONAL STACKED NONVOLATILE SEMICONDUCTOR MEMORY”, filed on Mar. 19,2009. Furthermore, the configuration is disclosed in U.S. patentapplication Ser. No. 12/406, 524, entitled THREE DIMENSIONAL STACKEDNONVOLATILE SEMICONDUCTOR MEMORY, filed on Mar. 18, 2009, U.S. patentapplication Ser. No. 12/679, 991, entitled “NON-VOLATILE SEMICONDUCTORMEMORY DEVICE AND METHOD FOR MANUFACTURING THE SAME”, filed on Mar. 25,2010, and U.S. patent application Ser. No. 12/532,030, entitled“SEMICONDUCTOR MEMORY AND METHOD FOR MANUFACTURING THE SAME”, filed onMar. 23, 2009. The U.S. patent applications described above are hereinincorporated by reference in their entirety.

1.1.3 Sense Amplifier Module 11

First, a configuration of the sense amplifier module 11 is describedreferring to FIG. 3. FIG. 3 is a schematic diagram illustrating a layoutof the sense amplifier module 11, and illustrates, for example, anaspect when viewed from the upper surface of the semiconductorsubstrate.

The sense amplifier module 11, as illustrated, includes multiple senseamplifier units SAU and multiple latch circuits XDL.

One sense amplifier unit SAU is provided for each bit line BL, andsenses/amplifies the data that is read into the corresponding bit lineBL, and furthermore transmits the write data to the corresponding bitline BL. As one example, 16 sense amplifier units SAU are arranged in aline along the direction along the bit line BL. In the followingdescription, SAU <0> to SAU <15> are used to respectively identify onesense amplifier unit among the 16 sense amplifier units.

One latch circuit XDL is also provided for each bit line BL, andtemporarily retains the data relating to the corresponding bit line BL.The latch circuit XDL is used for cache operation of the NAND flashmemory 1. That is, the multiple latch circuits (e.g. SDL, UDL, and LDL),described below, are included inside the sense amplifier unit SAU, andeven though these latch circuits are in use, the NAND flash memory 1 canreceive the data from the outside when the latch circuit XDL is empty. Aset of 16 latch circuits XDL are provided (this is expressed as XDL<15:0> in FIG. 3), and they are arranged in a line with the 16 senseamplifier units SAU, which are also arranged in a line, along thedirection of the bit line. One data input/output unit (I/O) correspondsto two lines of the sense amplifier units SAU and the latch circuitsXDL, that is, 32 bit lines BL.

FIG. 4 is a schematic diagram of a set of the sense amplifier units SAUand the latch circuits XDL that are arranged in a line, and illustratesthe configuration of the sense amplifier module 11 in more detail.

In addition to the sense amplifier unit SAU and the latch circuit XDL,which are described above, the sense amplifier module 11, asillustrated, includes a bus LBUS, a charge circuit 20, and a dischargecircuit 22.

Each of the sense amplifier unit SAU includes a sense amplifier sectionSA, and three latch circuits SDL, UDL, and LDL. The sense amplifiersection SA senses/amplifies the data that is read into the bit line BL,and furthermore applies a voltage to the bit line BL depending on thewrite data. That is, the sense amplifier section SA is a module thatdirectly controls the bit line BL. The latch circuits SDL, UDL and LDLretain data temporarily. At the time of data writing, the senseamplifier section SA controls the bit line BL depending on the dataretained by the latch circuit SDL among the three latch circuits. Theother latch circuits UDL and LDL are used for a multi-value operation inwhich the individual memory cell transistor retains two or more bitdata, or are used to perform a so-called quick pass write operation.

In each sense amplifier unit SAU, the sense amplifier section SA, andthe three latch circuits SDL, UDL, and LDL are connected by the bus LBUSin a manner that enables them to mutually transmit and receive the data.In an example in FIG. 4, the bus LBUS is commonly connected between thetwo sense amplifier units SAU that are adjacent in the bit linedirection and is arranged in such a manner as to cross the two senseamplifier units SAU in the direction along the bit line. Therefore, 8buses LBUS are provided for every 16 sense amplifier units SAU <15:0>.

A bus DBUS connects the sense amplifier unit SAU and the correspondinglatch circuit XDL in a manner that enables them to mutually transmit andreceive the data. In the example in FIG. 4, the 16 sense amplifier unitsSAU, arranged in a line, share one data bus.

The charge circuit 20 charges the bus DBUS. The charge circuit 20includes, for example, a low-resistance-to-voltage n channel MOStransistor 21, one end of the electric current path is connected to thebus DBUS, and a control signal DPC is applied to a gate.

The discharge circuit 22 discharges the bus DBUS. The discharge circuit22 includes, for example, a low-resistance-to-voltage n channel MOStransistor 23, one end of the electric current path is connected to thebus DBUS, the other end is grounded (GND), and a control signal DDS isapplied to a gate.

FIG. 5 is a circuit diagram of the sense amplifier unit SAU and morespecifically illustrates a configuration of the sense amplifier unitSAU.

The sense amplifier unit SAU, as described above, includes the senseamplifier section SA, and the three latch circuits SDL, LDL, and UDL.The sense amplifier unit SAU further includes a charge circuit 30 and abus switch 32.

The charge circuit 30 charges the bus LBUS. The charge circuit 30includes, for example, a low-resistance-to-voltage n channel MOStransistor 31, one end of the electric current path is connected to thebus LBUS, and a control signal LPC is applied to a gate. Then, thecharge circuit 30 charges the bus LBUS to a voltage lower than a powersource voltage VDDSA used in the sense amplifier unit SAU.

The bus switch 32 connects the bus DBUS and the bus LBUS. That is, thebus switch 32 includes, for example, a low-resistance-to-voltage nchannel MOS transistor 33, and in the bus switch 32, one end of theelectric current path is connected to the bus DBUS, the other end isconnected to the bus LBUS, and a control signal DSW is applied to agate.

Next, configurations of the sense amplifier section SA and the latchcircuits SDL, LDL, and UDL are described.

The sense amplifier section SA includes a high-resistance-to-voltage nchannel MOS transistor 40, low-resistance-to-voltage n channel MOStransistors 41 to 50, a low-resistance-to-voltage p channel MOStransistor 51, and a capacitor element 52.

A signal BLS is applied to a gate of the transistor 40, and one end ofthe electric current path is connected to the corresponding bit line BL.In the transistor 41, one end of the electric current path is connectedto the other end of the electric current path of the transistor 40, asignal BLC is applied to a gate, and the other end of the electriccurrent path is connected to a node SCOM. The transistor 41 clamps thecorresponding bit line BL to an electric potential depending on thesignal BLC.

In the transistor 45, one end of the electric current path is connectedto the node SCOM, the other end is connected to a node SRCGND (forexample, 0 V), and a gate is connected to a node INV_S. In thetransistor 42, one end of the electric current path is connected to thenode SCOM, the other end is connected to a node SSRC, and a controlsignal BLX is input to a gate. In the transistor 51, one end of theelectric current path is connected to a node SSRC, a power sourcevoltage VDDSA is applied to the other end, and a gate is connected tothe node INV_S. In the transistor 43, one end of the electric currentpath is connected to the node SCOM, the other end is connected to a nodeSEN, and a control signal XXL is input to a gate. In the transistor 44,one end of the electric current path is connected to the node SSRC, theother end is connected to the node SEN, and a control signal HLL isinput to a gate. In the capacitor element 52, one electrode is connectedto the node SEN, and a clock CLK is input to the other electrode. In thetransistor 47, one end of the electric current path is grounded, and agate is connected to the node SEN. In the transistor 48, one end of theelectric current path is connected to the other end of the electriccurrent path of the transistor 47, the other end is connected to the busLBUS, and a control signal STB is input to a gate.

In the transistor 46, one end of the electric current path is connectedto the node SEN, the other end is connected to the bus LBUS, and acontrol signal BLQ is input to a gate. In the transistor 50, one end ofthe electric current path is grounded, and a gate is connected to thebus LBUS. In the transistor 49, one end of the electric current path isconnected to the other end of the electric current path of thetransistor 50, the other end is connected to the node SEN, and a controlsignal LSL is input to a gate.

Next, the latch circuit SDL is described. The latch circuit SDL, asillustrated in FIG. 5, includes low-resistance-to-voltage n channel MOStransistors 60 to 63 and low-resistance-to-voltage p channel MOStransistors 64 to 67.

In the transistor 60, one end of the electric current path is connectedto the bus LBUS, the other end is connected to a node LAT_S, and acontrol signal STL is input to a gate. In the transistor 61, one end ofthe electric current path is connected to the bus LBUS, the other end isconnected to a node INV_S, and a control signal STI is input to a gate.In the transistor 62, one end of the electric current path is grounded,the other end is connected to a node LST_S, and a gate is connected tothe node INV_S. In the transistor 63, one end of the electric currentpath is grounded, the other end is connected to the node INV_S, and agate is connected to a node LAT_S. In the transistor 64, one end of theelectric current path is connected to the node LST_S, and a gate isconnected to the node INV_S. In the transistor 65, one end of theelectric current path is connected to the node INV_S, and a gate isconnected to the node LAT_S. In the transistor 66, one end of theelectric current path is connected to the other end of the electriccurrent path of the transistor 64, the power source voltage VDDSA isapplied to the other end, and a control signal SLL is input to a gate.In the transistor 67, one end of the electric current path is connectedto the other end of the electric current path of the transistor 65, thepower source voltage VDDSA is applied to the other end, and a controlsignal SLI is input to a gate.

In the latch circuit SDL, a first inverter is configured from thetransistors 62 and 64, and a second inverter is configured from thetransistors 63 and 65. Then, an output of the first inverter and aninput of the second inverter (the node LAT_S) are connected to the busLBUS via the transistor 60 for data transmission, and an input of thefirst inverter and an output of the second inverter (the node INV_S) areconnected to the bus LBUS via the transistor 61 for data transmission.The latch circuit SDL retains data in the node LAT_S and retains itsinversion data in the node INV_S.

Because the latch circuits LDL and UDL have the same configuration asthe latch circuit SDL, the description is omitted, but a referencenumeral and a control signal name of each transistor are described belowin such a manner as to be distinguishable from the reference numeral andthe control signal name of the latch circuit SDL as in FIG. 5.

Next, operation of the sense amplifier unit SAU with the configurationdescribed above is briefly described. First, a data writing operation isdescribed. If data is written to the memory cell transistor MT (if athreshold is increased by injecting an electric charge), an “H” level(data “1”) is stored in the node INV_S of the latch circuit SDL. As aresult, the transistor 45 is set to an ON state and the bit line BL isset to 0 V. On the other hand, if data is not written to the memory celltransistor MT (if the threshold is not changed with no electric chargebeing injected), an “L” level (data “0”) is stored in the node INV_S ofthe latch circuit SDL. As a result, the transistor 51 is set to an ONstate, and a predetermined positive voltage is applied to the bit lineBL.

Next, a read operation is described. At the time of read, first, thenode INV_S is set to an “L” level and the transistor 51 is set to the ONstate. Then, the bit line BL is charged by the transistor 51 via thetransistors 40 to 42. Furthermore, the transistor 44 is also set to theON state, and the node SEN is charged up to a predetermined electricpotential.

Thereafter, the transistor 44 is set to the OFF state, the signal XXL isat the “H” level and thus the transistor 43 is set to the ON state.Then, if the corresponding memory cell is in the ON state, the electricpotential of the node SEN is decreased, and the transistor 47 is in theOFF state. On the other hand, if the corresponding memory cell is in theOFF state, the electric potential of the node SEN maintains the “H”level, and as a result, the transistor 47 is in the ON state.

Then, the signal STB is set to the ON state, the electric potential thatdepends on the ON/OFF state of the transistor 47 is read into the busLBUS and is retained in any one of the latch circuits SDL, LDL, and UDL.

Next, a configuration of the latch circuit XDL is described referring toFIG. 6. FIG. 6 is a schematic diagram illustrating a circuitconfiguration of the latch circuit XDL and illustrating a connectionrelationship between the sense amplifier module SAU and the latchcircuit XDL.

The latch circuit XDL, as illustrated, includeslow-resistance-to-voltage n channel MOS transistors 90 to 94 andlow-resistance-to-voltage p channel MOS transistors 95 to 99.

In the transistor 90, one end of the electric current path is connectedto the bus XBUS that is connected to the input and output circuit 13,the other end is connected to a node LAT_X, and a control signal XTL isinput to a gate. In the transistor 91, one end of the electric currentpath is connected to the bus DBUS, the other end is connected to a nodeINV_X, and a control signal XTI is input to a gate. In the transistor92, one end of the electric current path is connected to the node LAT_X,and a gate is connected to the node INV_X. In the transistor 93, one endof the electric current path is grounded, the other end is connected tothe other end of the electric current path of the transistor 92, and acontrol signal XNL is input to a gate. In the transistor 95, one end ofthe electric current path is connected to the node LAT_X, and a gate isconnected to the node INV_X. In the transistor 96, one end of theelectric current path is connected to the node INV_X, and a gate isconnected to the node LAT_X. In the transistor 97, one end of theelectric current path is connected to the other end of the electriccurrent path of the transistor 95, the power source voltage VDDSA isapplied to the other end, and a control signal XLL is input to a gate.In the transistor 98, one end of the electric current path is connectedto the other end of the electric current path of the transistor 96, thepower source voltage VDDSA is applied to the other end, and a controlsignal XLI is input to a gate.

In this manner, the latch circuit XDL also has the substantially sameconfiguration as the latch circuit SDL and the like, but the latchcircuit XDL retains the data between the bus DBUS and the bus XBUS.

Furthermore, as described above, in the present example, the 16 senseamplifier modules SAU <15:0> and the 16 latch circuits XDL <15:0> areconnected by one bus DBUS. A connection between the sense amplifier unitSAU and the bus DBUS is switched on and off by a first switch SW1, and aconnection between the latch circuit XDL and the bus DBUS is switched onand off by a second switch SW2. Therefore, the data transmission betweenthe latch circuit XDL and the sense amplifier unit is performed by 16time division transmission operations.

1.2 Operation of Transmitting Data Between Latches Inside SenseAmplifier Unit

Next, an operation of transmitting data among the latch circuits SDL,LDL, and UDL according to the present embodiment is described. A casewhere the data is transmitted from the latch circuit SDL to the latchcircuit LDL is described below as one example, referring to FIG. 7 andFIG. 8. FIG. 7 is a flowchart at the time of data transmissionoperation, and FIG. 8 is a timing chart for the various signals at thattime.

As illustrated, the data transmission operation from SDL to LDLgenerally includes two steps. The first step is an operation ofresetting LDL and an operation of storing data “1” in LDL. Next, thesecond step is an operation of actually transmitting the data from SDLto LDL. The operation described below is performed, for example, underthe control of the control circuit 14, and the various control signalsdescribed referring to FIG. 5 and FIG. 6 are included, for example, inthe control signal 14.

As illustrated in FIG. 7, the control circuit 14 first sets the signalDSW to the “H” level, and thus connects the bus DBUS to any one of thebuses LBUS. Moreover, the control circuit 14 sets the signal DDS to the“H” level, and discharges the bus DBUS and the LBUS (Step S10 and apoint in time t0). Because of this, electric potentials of the bus DBUSand the LBUS are at approximately 0 V. Additionally, the electricpotentials of the signals DSW and DDS, which are set to the “H” level,are VDDSA, the power source voltage of the latch circuits SDL, LDL, UDL.In the present specification, the same is true for the other controlsignals, except as described specifically otherwise.

Next, LDL, a data transmission destination, fetches the data on the busLBUS (Step S11). That is, the control circuit 14 sets the signals LLLand LLI to the “L” level and to the “H” level, respectively, (a point intime t1), and thus the transistors 76 and 77 are set to the ON state andthe OFF state, respectively, (the point in time t1). Subsequently, thecontrol circuit 14 sets the signal LTI to the “H” level (a point in timet2). The state of the SAU at this time is illustrated in FIG. 9, thecircuit diagram. As illustrated, the transistor 71 is in the ON state,and the electric potential of the bus LBUS is brought into LDL. That is,the node INV_L is at the “L” level, and the node LAT_L is set to the “H”level (VDDSA).

When the first step as described above is completed, the control circuit14 subsequently proceeds to the second step. The second step isdescribed below, further referring to the circuit diagram of FIG. 10.

First, the control circuit 14 sets the signal DSW to the “L” level, andseparates DBUS from LBUS (Step S12 and a point in time t3).Subsequently, the control circuit 14 sets the signal LPC to the “H”level, and charges the bus LBUS (Step S13 and a point in time t4). Atthis time, the control circuit 14 controls the transistor 31 in such amanner that the electric potential of the bus LBUS is at (Vclh−Vt).(Vclh−Vt), for example, is approximately 0.5 to 1 V. The voltage Vclh isa voltage that is smaller than power source voltage VDDSA of the senseamplifier unit SAU, and Vt is a threshold voltage of thelow-resistance-to-voltage n channel transistor (for example, thetransistors 31, 60, 61, 70, 71, 80, 81 and so forth) inside the senseamplifier unit SAU. Because of this, for example, the control circuit 14sets the electric potential of the signal LPC to Vclh. Because of thisthe electric potential of the bus LBUS is clamped to (Vclh−Vt).Otherwise, the electric potential of the signal LPC may be sufficientlyincreased and Vclh may be applied to the other end of the electriccurrent path of the transistor 31.

Next, SDL outputs retention data on to the bus LBUS, and LDL fetches theretention data (Step S14). That is, the control circuit 14 sets thesignal LLL to the “H” level during a period when the signal LPC is setto the “H” level (a point in time t5). Because of this, the electricpotential of the node LAT_L of LDL is set to a state of floating atVDDSA. Then, the control circuit 14 sets the signals STL and LTL to the“H” level after setting the signal LPC to the “L” level (a point in timet6). Moreover, electric potentials Vclm and Vcll of the signals STL andLTL are also made smaller than VDDSA. Moreover, the relation to Vclh isas follows.

Vclh≧Vclm≧Vcll

Vclh>Vcll

where Vclh≧Vclm (preferably, Vclh>Vclm) is a condition for SDL tostabilize and thus retain the data “1”, and Vclh≧Vcll (preferably,Vclh>Vcll) is a condition for LDL to stabilize and thus retain the data“1”. That is, the reason is as follows. If SDL and LDL retain the “H”level, when a gate voltage of the transmission transistors 60 and 70 isexcessively high, there is concern that the transistors will be in theON state, and the retention data in the SDL and LDL will be damaged.

Furthermore, as one example, values of Vclh, Vclm, and Vcll are set asfollows.

Vclh=1 V+Vt

Vclm=0.75 V+Vt

Vcll=0.5 V+Vt

The signal STL is set to the “H” level, and thus the electric potentialof the bus LBUS changes depending on the retention data in SDL (the datain LAT_S). When SDL retains the data “1”, the transistor 60 is in acut-off state, and the electric potential of the bus LBUS maintains the“H” level (Vclh−Vt). On the other hand, when SDL retains the data “0”,the transistor 60 is in the ON state, and the electric potential of thebus LBUS transitions to the “L” level (0 V) (the point in time t6).

Furthermore, the signal LTL is set to the “H” level (Vcll).Consequently, when the bus LBUS transitions to the “L” level (0 V), thetransistor 70 is in the ON state, and the “L” level is stored in thenode LAT_L. On the other hand, when the bus LBUS maintains the “H” level(Vclh−Vt), the transistor 70 is still in the OFF state. Therefore, thenode LAT_L continues to retain the “H” level (VDDSA).

In this manner, the data “1” is made to be retained in the transmissiondestination, the latch circuit, and thereafter the transmissiondestination, the latch circuit, outputs the data. At this time, if thetransmission data is “0”, an input switch (the transistor 70) of thetransmission destination, the latch circuit, is turned on, and thus thedata “0” is transmitted to the transmission destination, the latchcircuit. On the other hand, if the transmission data is “1”, the inputswitch is turned off, and thus the transmission destination, the latchcircuit is set to an unchangeable state.

1.3 Effects According to Present Embodiment

When the configuration according to the first embodiment is provided,reliability of operation of the NAND flash memory 1 can be improved. Thepresent effect is described below.

As described above, in the NAND flash memory, a bit line control section(the sense amplifier section SA in FIG. 4) that directly controls theelectric potential of the bit line, and multiple data latches (SDL, UDL,LDL, and XDL in FIG. 4) are provided for one bit line. The number ofnecessary data latches changes depending on the multi-value extent ofthe cell, the presence or absence of the cache operation, or whether ornot the high speed operation is supported, but is generally 3 to 5. Thedata transmission between the data latches is performed via the data busline (LBUS and DBUS in FIG. 4). At this time, the data bus lineundergoes a considerable amount of charging and discharging. The reasonsfor that are that several KB sense amplifier and data latches arepresent inside the chip and several KB data bus line operates at thetime of data transmission, and additionally because a wiring length ofthe data bus line is long and a wiring interval is narrow, a parasiticcapacitance is increased and thus charging/discharging is necessary tobe performed and enormous load capacity is handled in total. Thisproblem is more serious as device sizes reduces even further, and alsoan architecture in which the sense amplifier is arranged under thememory cell array has the same problem as the NAND flash memory in whichthe memory cells are stacked in three dimensions.

In view of the situation described above, according to the presentembodiment, power consumption is reduced by attempting to make data buslow in amplitude and thus reducing the amount of charging/discharging ofthe data bus. More specifically, while maintaining VDDSA as the powersource of the data latch itself, the data bus is amplified with avoltage (Vclh−Vt) that is smaller than VDDSA, without using VDDSA. Atthis time, the gate electric potential of the transistor 31 that chargesthe data bus may be set to a predetermined voltage (for example, Vclh)that is lower than VDDSA and thus may clamp the electric potential ofthe data bus to (Vclh−Vt), or may use a transmission gate type thattransmits this clamp voltage. As a result, the power consumption in thedata bus can be reduced to ½ to ¼ of the previous power consumption.

Furthermore, at the same time, the gate electric potential of thetransmission transistor (the transistors 60, 61, 70, 71, 80, and 81 inFIG. 5) of the data latch is set to a predetermined voltage (forexample, Vclm and Vcll) that is lower than VDDSA. Because of this, amalfunction of the transmission transistor due to a decrease in thecharge voltage of the data bus can be prevented and operationalstability of the data latch can be improved.

2. Second Embodiment

Next, a semiconductor memory device according to a second embodiment isdescribed. In the present embodiment, the charge on the bus LBUS iscarried out by a transmission destination, a latch circuit, withoutusing a charge circuit 30 of the first embodiment described above. Onlythe parts of the present embodiment that differ from the firstembodiment are described below.

2.1 Operation of Transmitting Data Between Latches Inside SensorAmplifier Unit

Data transmission operation according to the present embodiment isdescribed. A case where data is transmitted from a latch circuit SDL toa latch circuit LDL in the same manner as in the first embodiment isdescribed below as one example, referring to FIG. 11 and FIG. 12. FIG.11 is a flowchart at the time of data transmission operation, and FIG.12 is a timing chart for various signals at that time.

As illustrated, after Steps S10 to S12 described in the firstembodiment, a control circuit 14 charges a bus LBUS by LDL (Step S20 andat time t7). This feature is illustrated in FIG. 13, a circuit diagram.FIG. 13 is a circuit diagram of a sense amplifier module during a periodof time from time t7 to time t8 in FIG. 12. That is, the control circuit14 sets a signal LTL to an “H” level with a signal LPC being set to an“L” level. An electric potential of the signal LTL is set to Vclhdescribed in the first embodiment. Then, because transistors 74 and 76are set to an ON state and thus a node LAT_L is substantially VDDSA, anelectric potential of the bus LBUS is clamped to (Vclh−Vt) by atransistor 70. (Vclh−Vt), for example, is 0.5 V to 1 V.

After the signal LTL is set to an “L” level at time t8, operation of thesignal LTL is the same as that in the first embodiment.

2.2 Effect According to Present Embodiment

According to the present embodiment, reliability of operation of theNAND flash memory can be further improved. As illustrated in the firstembodiment, as a data bus line is made lower in amplitude, powerconsumption is reduced even more. However, on the other hand, when lowamplification is excessive, there is a likelihood that a data changedefect will take place, for example, by variance in a threshold of atransistor that determines a charge level of a data line and variance ina threshold of a transistor of a latch, a data receiver.

In the present embodiment, an occurrence of this type of defect can beprevented. The present effect is described referring to FIG. 14 and FIG.15. FIG. 14 is a graph illustrating electric potentials of the signalsLPC and LTL, and the bus LBUS, and FIG. 15 is a circuit diagram of oneregion of a sense amplifier unit SAU.

If charge of the bus LBUS is performed with voltage clamp by the chargecircuit 30, the electric potential of the bus LBUS is influenced by theelectric potential of the signal LPC. For example, as illustrated inFIG. 14, the fact that a threshold of a transistor 31 for LBUS chargevaries among high values means that the electric potential of the signalLPC is decreased, and as a result, the electric potential of the busLBUS is also decreased. Furthermore, the fact that a threshold of thetransistor 70 of the latch circuit LDL varies among low values meansthat the signal LTL is increased. In this manner, when a situationoccurs in which the electric potential of the bus LBUS is decreased, andthe electric potential of the signal LTL is increased, there is alikelihood that the transistor 70 will be erroneously in the ON state.When the transistor 70 is in the ON state, there is concern that avoltage VDDSA retained in the node LAT_L will drop into the bus LBUS,and LDL will lose data.

Accordingly, the method according to the present embodiment can solvethe problem described above by performing the charge on the bus LBUSwith the latch circuit, the data receiver. That is, as described in FIG.12, during the period of time from time t7 to time t8, the bus LBUS ischarged by the transistor 70. Even if the electric potential of LBUS isset to a low value due to the variance in the threshold of thetransistor 70, when the signal LTL is set to the “H” level thereafter,an effect that the signal LTL is decreased due to the variance in thethreshold can be obtained. In other words, an influence of the variancein the threshold on the LBUS charge and an influence of the variance inthe threshold on the data transmission are offset against each other. Inthis manner, a decrease in the reliability of operation due to thevariance in the threshold of the transistor can be prevented.

Furthermore, the method according to the present embodiment can reducethe charge level of the bus LBUS. Because of this, the power consumptioncan be reduced. FIG. 16 is a graph making a comparison between thecharge levels of the buses LBUS according to the first embodiment andthe second embodiment.

As illustrated, in the method according to the first embodiment, thecharge level is, for example, 1 V. The charge level is broken down intoa variance in a threshold of the transistor in a path between aregulator supplying various voltages and the sense amplifier unit SAU,noise, a leak, a variance in a threshold of the transitor inside thesense amplifier unit SAU, and a margin. In this regard, according to thepresent embodiment, for the reason described above, there is no need totake into consideration the variance in the threshold of the transistorinside the sense amplifier unit SAU. As a result, the charge level canbe set to, for example, approximately 0.7 V, which is lower than in thefirst embodiment.

3.3 Third Embodiment

Next, a semiconductor memory device according to a third embodiment isdescribed. The present embodiment results from the charge circuit 30assisting charge of a bus LBUS in the second embodiment described above.In other words, the present embodiment is equivalent to making anelectric potential of a signal LPC smaller than Vclh with the first andsecond embodiments being combined. Only the parts of the presentembodiment which differ from the first and second embodiments aredescribed below.

3.1 Operation of Transmitting Data Between Latches Inside SensorAmplifier Unit

A case where data is transmitted from SDL to LDL in the same manner asin the first and second embodiments is described as an example of a datatransmission operation according to the present embodiment, referringFIG. 17 and FIG. 18. FIG. 17 is a flowchart at the time of datatransmission operation, and FIG. 18 is a timing chart for varioussignals at that time.

As illustrated, after Steps S10 to S12 described in the firstembodiment, a control circuit 14 sets the signal LPC to an “H” level(Step S30 and at time t4). However, unlike in the first embodiment, anelectric potential of the signal LPC is Vcla, and furthermore Vcla≦Vclh(preferably, Vcla<Vclh). As a result, an electric potential of the busLBUS is increased up to (Vcla−Vt).

Next, the control circuit 14 sets the signal LPC to an “L” level andcharges the bus LBUS by LDL (Step S20 and at time t7). As a result, asdescribed in the second embodiment, the electric potential of the busLBUS is charged to (Vclh−Vt).

An operation after a signal LTL is set to the “L” level at time t8 isthe same as in the first embodiment.

3.2 Effect According to Present Embodiment

In the method according to the present embodiment, reliability ofoperation of a NAND flash memory can be further improved. The presenteffect is described referring to FIG. 19. FIG. 19 is a circuit diagramof a sense amplifier unit SAU, and illustrates its operation whencharging a bus LBUS.

According to the present embodiment, the charge of the bus LBUS isperformed in two steps. That is, first, the charge circuit 30 increasesthe electric potential of the bus LBUS up to (Vcla−Vt). Thereafter, LDLincreases the bus LBUS up to (Vclh−Vt) that is a final value. In thepresent method, stability of operation of a latch circuit can beimproved.

For example, when LDL charges the bus LBUS, a ratio of an ON resistanceof a series part of transistors 74 and 76 in FIG. 19 and an ONresistance of a transistor 70 is important. When the ON resistance ofthe transistor 70 is excessively low, when the transistor 70 is turnedon, an electric potential of a node LAT_L between the transistor 74 andthe transistor 70 is drastically decreased. As a result, there isconcern that the electric potential of the node LAT_L will exceed athreshold of an inverter that is made from transistors 73 and 75 (thetransistor 73 will transition from ON to OFF, and the transistor 75 willtransition from OFF to ON), and retention data in a latch circuit LDLwill be inverted.

In this respect, according to the second embodiment, when the transistor70 is turned on, because the electric potential of the bus LBUS is 0 V,a voltage VGS between a gate and a source of the transistor 70 (thesource is LBUS) is large and the ON resistance is comparatively small.

In contrast, according to the present embodiment, when the transistor 70is turned on, the bus LBUS has been already charged to (Vcla−Vt).Therefore, VGS of the transistor 70 is lower and the On resistance ishigher than in the second embodiment. Accordingly, stability of thelatch circuit LDL can be improved, compared to the second embodiment.This is true for the other latch circuits SDL and UDL.

Furthermore, a charge level described referring to FIG. 16 can bereduced more than in the first embodiment.

4. Fourth Embodiment

Next, a semiconductor memory device according to a fourth embodiment isdescribed. In the present embodiment, charging of a bus LBUS in thefirst to third embodiments is omitted. Only the parts of the presentembodiment that differ from the first to third embodiments are describedbelow.

4.1 Operation of Transmitting Data Between Latches Inside SensorAmplifier Unit

A case where data is transmitted from SDL to LDL in the same manner asin the first to third embodiments is described as an example of datatransmission operation according to the present embodiment, referring toFIG. 20 and FIG. 21. FIG. 20 is a flowchart at the time of datatransmission operation, and FIG. 21 is a timing chart for varioussignals at that time.

As illustrated in FIG. 20, a processing flow according to the presentembodiment is equivalent to removing Step S13 in FIG. 7 described in thefirst embodiment. That is, as illustrated in FIG. 21, when the bus DBUSand the bus LBUS are disconnected, in a state where an electricpotential of LBUS is 0 V, signals STL and LTL are set to an “H” level(at time t6). Then, the electric potential of the bus LBUS maintains 0 Vdepending on an electric potential of a node LAT_S, or is increased upto (Vclh−Vt).

The others are the same as in the first to third embodiments.

4.2 Effect According to Present Embodiment

If a capacity of the bus LBUS is small, as in the method according tothe present embodiment, electric potentials of data transmissionvoltages STL and LTL are made smaller than a power source voltage VDDSA,and thus charge of LBUS can become unnecessary.

The reason for this is the same as the reason described above in thethird embodiment. That is, according to the third embodiment, by turningon a transistor 70 after charging the bus LBUS, a transistor VGS is madesmaller and thus data inversion in a latch circuit is prevented. Incontrast, according to the present embodiment, a gate electric potentialof the transistor 70 is lowered and thus VGS of the transistor isdecreased. As a result, an On resistance of the transistor 70 can beincreased, and stability of a latch circuit LDL can be improved. This isalso true for the other latch circuits SDL and UDL.

5. Fifth Embodiment

Next, a semiconductor memory device according to a fifth embodiment isdescribed. The present embodiment results from a charge circuit 30assisting charge of a bus LBUS in the fourth embodiment described above.In other words, the present embodiment is equivalent to making anelectric potential of a signal LPC smaller than Vclh in the firstembodiment. Only the parts of the present embodiment that differ fromthe fourth embodiment are described below.

5.1 Operation of Transmitting Data Between Latches Inside a SenseAmplifier Unit

A case where data is transmitted from SDL to LDL in the same manner asin the first to third embodiments is described as an example of datatransmission operation according to the present embodiment, referring toFIG. 22 and FIG. 23. FIG. 22 is a flowchart at the time of datatransmission operation, and FIG. 23 is a timing chart for varioussignals at that time.

As illustrated in FIG. 22, a processing flow according to the presentembodiment is equivalent to adding processing in Step S30, immediatelybefore Step S14 in FIG. 20 described in the fourth embodiment. That is,as illustrated in FIG. 23, when the bus DBUS and the bus LBUS aredisconnected, a control circuit 14 sets the signal LPC to an “H” level(Step S30 and a point in time t4). An electric potential of the signalLPC is Vcla as described in the third embodiment. As a result, anelectric potential of the bus LBUS is increased up to (Vcla−Vt).

Thereafter, signals STL and LTL are set to the “H” level without furtherperforming charge on the bus LBUS (a point in time t6). Then, theelectric potential of the bus LBUS is decreased to 0 V, or is increasedup to (Vclh−Vt), depending on an electric potential of a node LAT_S.

The others are the same as in the first to third embodiments.

5.2 Effect According to Present Embodiment

According to the present embodiment, while the charge of the bus LBUSbecomes unnecessary, stability of operation of a latch circuit can beimproved as described in the third embodiment.

6. Sixth Embodiment

Next, a semiconductor memory device according to a sixth embodiment isdescribed. The present embodiment results from applying the first tofifth embodiments to data transmission between a latch circuit inside asense amplifier unit SAU and a latch circuit XDL. Only the parts of thepresent embodiment that differ from the first to fifth embodiments aredescribed below. Furthermore, a case where data is transmitted from thelatch circuit XDL to the latch circuit LDL is described below as anexample.

6.1 First Data Transmission Example

First, a first data transmission example is described referring to FIG.24 and FIG. 25. The present example results from applying the methoddescribed in the first embodiment for the data transmission from XDL toLDL.

As illustrated in the first embodiment, a data transmission operationgenerally includes two steps. In a case of the data transmission fromXDL to LDL, the first step is an operation of resetting LDL, and data“0” is stored in LDL. The second step that is performed is an operationof actually transmitting data from XDL to LDL.

As illustrated in FIG. 24, first, processing in Step S10 is performed,and, next, processing in Step S40 is performed. In Step S40, a controlcircuit 14 sets a signal LTL to an “H” level (at time t2). As a result,a node INV_L of the latch circuit LDL is set to the “H” level (VDDSA).

Next, processing in Step 41 is performed. That is, the control circuit14 sets signals LPC and DPC to the “H” level (at time t4). Electricpotentials of the signals LPC and DPC are Vclh, as described above. As aresult, electric potentials of buses DBUS and LBUS are set to (Vclh−Vt).Moreover, like the transistor 31, the transistor 21, which charges DBUS,may be a type that clamps a voltage to (Vclh−Vt), or may be atransmission gate type.

Next, a latch circuit XDL outputs retention data on the buses DBUS andLBUS, and LDL fetches the retention data (Step S42). That is, thecontrol circuit 14 sets a signal LLI to the “H” level (at time t5).Because of this, an electric potential of the node INV_L of LDL is setto a floating state at VDDSA. Thereafter, the control circuit 14 setssignals XTI and LTI to the “H” level (at time t6). Moreover, electricpotentials of a signal XTL and the signal LTL are Vclm and Vcll, whichare described above, respectively.

Inverted data (data in INV_X) retained by XDL is output to the busesDBUS and LBUS by setting a signal XTI to the “H” level. When XDL retainsdata “1” (INV_V=“L”), a transistor 91 is in an ON state and electricpotentials of the buses DBUS and LBUS transition to an “L” level (0 V).On the other hand, when XDL retains the data “0” (INV_X=“H”), thetransistor 91 is in a cut-off state, and the electric potentials of thebuses DBUS and LBUS maintain the “H” level (Vclh−Vt).

Furthermore, a signal LTI is set to the “H” level (Vcll). Consequently,when the bus LBUS transitions to the “L” level (0 V), a transistor 70 isin the ON state, and the “L” level is stored in the node INV_L. On theother hand, when the bus LBUS maintains the “H” level (Vclh−Vt), thetransistor 70 is in a cut-off state. Therefore, a node INV_L continuesto retain the “H” level (VDDSA).

In this manner, in a case of the present example, because the node INV_Xthat retains inverted data of XDL is connected to the bus DBUS, when thedata is transmitted from XDL to LDL, the signal LTI is set to the “H”level, contrary to the fact that, according to the first embodiment, thesignal LTL is set to the “H” level. In other words, the inverted dataretained by XDL is transmitted to the node INV_L that retains theinverted data retained by LDL.

Moreover, this is true for a case where the data is transmitted from asense amplifier unit SAU to XDL. In XDL, as in SDL, LDL, and UDL, an nchannel MOS transistor (a transistor 91) is used for a transmission gatein order to reduce an occupation area inside a chip. Therefore, when the“H” level is transmitted, an electric potential of transmission data isdecreased by a threshold of the transistor 91. Thus, when the data istransmitted from the sense amplifier unit SAU to XDL, first, XDL ischarged (reset), and thereafter INV_X is charged/discharged depending ondata in DBUS.

More specifically, the data is first forcibly input from XBUS to XDL andINV_X is set to the “H” level. Thereafter, the transistor 91 is turnedon or off depending on the electric potential of DBUS.

Furthermore, in the present example, Step S41 may be removed. Thepresent example is equivalent to applying the method described in thefourth embodiment to the data transmission from XDL to LDL.

6.2 Second Data Transmission Example

Next, a second data transmission example is described referring to FIG.26. The present example results from applying the method described inthe third embodiment for the data transmission from XDL to LDL. Withregard to the detail of processing, because FIG. 17 is applied to FIG.24, a flowchart is omitted.

As illustrated in FIG. 26, in the second step, signals LPC and DPC areset to an “H” level, as in Step S41 described in FIG. 24 (a point intime t4). This electric potential is Vcla as described in the thirdembodiment. As a result, electric potentials of buses DBUS and LBUS areincreased from 0 V up to (Vcla−Vt).

Subsequently, the buses DBUS and LBUS are charged by LDL as described inStep S20 in the third embodiment. That is, a signal LTI is set to the“H” level (a point in time t7). An electric potential of the signal LTIis Vclh. As a result, the electric potentials of the buses DBUS and LBUSare increased from (Vcla−Vt) to (Vclh−Vt).

Thereafter, a signal XTI and the signal LTI are set to the “H” level asin the first data transmission example (a point in time t6). Theelectric potentials are Vclm and Vcll, respectively.

Furthermore, electric potentials of the signals LPC and DPC may be setto Vcla. The example corresponds to the fifth embodiment.

Furthermore, in the present example, the signals LPC and DPC may bemaintained at an “L” level. The example is equivalent to applying themethod described in the second embodiment for the data transmission fromXDL to LDL.

6.3 Third Data Transmission Example

Next, a third data transmission example is described. In the first andsecond examples, the simple data transmission from XDL to LDL isdescribed. However, the first to fifth embodiments can be used for amathematical operation, data manipulation and the like among latches.Because the third data transmission example relates to such a case, acase where the third embodiment is applied to an operation oftransmitting inverted data from XDL to LDL is described as one example.Of course, it is possible to apply the first, second, fourth, or fifthembodiment.

FIG. 27 is a timing chart for various signals according to the thirddata transmission example. As illustrated, in the first step, a signalLTI is set to an “H” level, and a node LAT_L of LDL is set to the “H”level (VDDSA).

Next, in the second step, signals LPC and DPC are set to Vcla, andsubsequently a signal LTL is set to Vclh, and electric potentials ofbuses DBUS and LBUS are charged up to (Vclh−Vt).

Thereafter, a signal XTI and the signal LTL are set to an “H” level. Theelectric potentials are Vclm and Vcll, respectively. As a result, data(inverted data) in a node INV_X of XDL are transmitted to a node LAT_Lof LDL.

6.4 Effect According to Present Embodiment

As described above, the method of transmitting data according to thefirst to fifth embodiments can be applied to various data transmissionand data manipulation.

7. Seventh Embodiment

Next, a semiconductor memory device according to a seventh embodiment isdescribed. The present embodiment relates to a configuration forgenerating a control signal of a sense amplifier unit SAU according tothe first to sixth embodiments described above. Only the parts of thepresent embodiment that differ from the first to sixth embodiments aredescribed below.

7.1 Configuration of Control Signal Generation Circuit

FIG. 28 is a circuit diagram of a control signal generation circuitaccording to the present embodiment. FIG. 28 illustrates in detail theconfiguration to generate voltages Vclh, Vclm, and Vcll givenspecifically as a control signal LPC, DPC or the like.

As illustrated, a control signal generation circuit 300 includes avoltage generation circuit 100 and a sense amplifier control circuit200.

The voltage generation circuit 100 includes variable resistance elements101 to 103, comparators 104 to 106, an electric current source 108 and alow-resistance-to-voltage n channel MOS transistor 109.

The transistor 109 has the same size as a transistor inside a senseamplifier unit SAU. More specifically, the transistor 109 has the samethreshold voltage as transmission transistors 60, 61, 70, 71, 80, and 81of latch circuits SDL, LDL, and UDL, a transistor 31 or the like, or hasthe same gate width. Then, a gate and a drain of the transistor 109 areconnected to a node N1 and the transistor 109 performs a functionequivalent to a function of a diode.

One end of the resistance element 101 is connected to a source of thetransistor 109, and the other end is grounded. The resistance element102 is connected between the node N1 and a node N2, and the resistanceelement 103 is connected between the node N2 and a node N3. Resistancevalues of the resistance elements 101 to 103 are controlled, forexample, by a control circuit 14 in such a manner to provide appropriatevoltages Vclh, Vclm and Vcll, respectively. The electric current source108 supplies a reference electric current Iref to the node N3.

The comparator 104 has an inverting input terminal connected to the nodeN1 and a non-inverting input terminal connected to an output terminal,and outputs the voltage Vcll equivalent to an electric potentialVcll_pre of the node N1. The comparator 105 has an inverting inputterminal connected to the node N2 and a non-inverting input terminalconnected to the output terminal, and outputs the voltage Vclmequivalent to an electric potential Vclm_pre of the node N2. Thecomparator 106 has an inverting input terminal connected to the node N3and a non-inverting input terminal connected to the output terminal, andoutputs the voltage Vclh equivalent to an electric potential Vclh_pre ofthe node N3.

The sense amplifier control circuit 200 receives the voltages Vclh, Vclmand Vcll from the voltage generation circuit 100, and furthermorereceives a control signal from the control circuit 14. Then, varioussignals SLL, SLI, STL, STI, LLL, LLI, LTL, LTI, ULL, ULI, UTL, UTI, LPC,DPC, BLS, BLC, BLX, XXL, HLL, STB, BLQ, LSL and the like for controllingthe sense amplifier unit SAU are generated based on the control signalfrom the control circuit 14.

Moreover, the control signal generation circuit 300 may be one part ofthe control circuit 14. In this case, a control unit inside the controlcircuit 14 supplies the control signal to the sense amplifier controlcircuit 200 and controls operation of the sense amplifier unit.

7.2 Effect According to Present Embodiment

According to the present embodiment, the voltages Vclh, Vclm, and Vcllused in the sense amplifier unit SAU are generated based on thetransistor 109 that has the same size as the transistor inside the senseamplifier unit SAU. In other words, the voltages Vclh, Vclm, and Vcllcan be generated while monitoring a variance in a threshold of thetransistor in the sense amplifier unit SAU. Therefore, it is possible toreflect influences of temperature dependability and a variance in athreshold of the transistor, and the like in the voltages Vclh, Vclm,and Vcll.

8. Modification Examples and Others

As described above, the semiconductor memory device according to thefirst to seventh embodiments includes the memory cell array thatincludes the multiple memory cells that are stacked on the semiconductorsubstrate, and the sense amplifier that can retain the data read from orto be written to the memory cell. The sense amplifier includes the busLBUS or DBUS that can transmit the data, the first latch circuit SDLthat includes the first transistor Tr60, the second latch circuit LDLthat includes the second transistor Tr70, and the third transistor 31 or21 that charges the bus. The first latch circuit SDL includes the firstdata retention units Tr62 and Tr64, and the first transistor Tr60 thatconnects the first data retention unit and the bus. The second latchcircuit LDL includes the second data retention units Tr72 and Tr74 andthe second transistor Tr70 that connects to second data retention unitand the bus. The third transistor 31 or 21 charges the bus. At the timewhen the data is transmitted from the first latch circuit SDL to thesecond latch circuit LDL, the third transistor 30 charges the bus LBUSto the electric potential (Vclh−Vt) or (Vcla−Vt) lower than the powersource voltage by applying the first voltage Vclh or Vcla lower than thepower source voltage VDDSA of the first and second latch circuits to thegate (t4 to t6 in FIG. 8). Moreover, after charging the bus, the secondand third voltages (STL=Vclm and LTL=Vcll) lower than the power sourcevoltage are applied to the gates of the first and second transistors 60and 70, respectively (t6 in FIG. 8).

Otherwise, when the third transistor is abandoned and the data istransmitted from the first latch circuit SDL to the second latch circuitLDL, the second latch circuit LDL charges the bus LBUS to the electricpotential (Vclh−Vt) lower than the power source voltage VDDSA byapplying the first voltage LTL=Vclh or Vcla lower than the power sourcevoltage VDDSA of the first and second latch circuits to the gate of thesecond transistor Tr70 (t7 to t8 in FIG. 12). Moreover, after chargingthe bus, the second and third voltages STL=Vclm and LTL=Vcll lower thanthe power source voltage are applied to the gates of the first andsecond transistors 60 and 70, respectively (t6 in FIG. 8).

Otherwise, when the data is transmitted from the first latch circuit SDLto the second latch circuit LDL, the first and second voltage STL=Vclhand LTL=Vcll lower than the power source voltage are applied to thegates of the first and second transistors 60 and 70, respectively,without charging the bus (t6 in FIG. 21).

According to the present configuration, the reliability of the operationof the semiconductor memory device can be improved. Moreover, theembodiments are not limited to the ones described above, and variousmodifications are possible. For example, according to the first to fifthembodiments described above, the example is described in which the datais transmitted from SDL to LDL, but the same method can be applied toall the data transmission between SDL, LDL, and UDL. Furthermore,according to the sixth embodiment, the data transmission from XDL to LDLis described as the example, but the same method can be applied to allthe data transmission between SDL, LDL and UDL and XDL.

Furthermore, the embodiments described above are not limited to thetransmission between the data latches in the NAND flash memory, and canbe widely applied to the data transmission between the latch circuits,each having a transmission gate. FIG. 29 is a circuit diagramillustrating a configuration in which two latch circuits L1 and L2 areconnected to each other with a data bus B1.

As illustrated, the latch circuit L1 is connected to the bus B1 with a nchannel transmission transistor Tr1, and the latch circuit L2 isconnected to the bus B1 with a n channel transmission transistor Tr2.Then, the bus B1 is driven by the power source voltage VDDSA that is thesame as the power source voltage of the latch circuits L1 and L2. Withthis configuration, it is assumed that the data is transmitted from thelatch circuit L1 to L2.

In this case, the latch L2, a transmission destination is set to an “H”level, and that input node IN2 is set to a state of floating at the “H”level. Then, the bus B1 is charged to VDDSA. Thereafter, data aretransferred to L2 by the latch circuit L1. The data transmission isperformed as follows. That is,

-   -   (1) a case where the “H” level is transmitted: Because the bus        B1 maintains the “H” level (VDDSA) and the transmission        transistor Tr2 (also Tr1) is in an OFF state, the latch circuit        L2 continues to retain the “H”, and    -   (2) a case where an “L” level is transmitted: Because the bus B1        is decreased to an “L” level (0 V), and the transmission        transistor Tr2 is in the ON state, retention data in the latch        circuit L1 transitions from the “H” level to the “L” level        (IN2=“L”).

The embodiments described above can be widely applied with respect tothe data transmission between such latch circuits. That is, asillustrated in FIG. 30, a bus drive voltage is decreased from VDDS to V1(equivalent to (Vclh−Vt) described in the embodiment). Because of this,the power consumption can be reduced. Moreover, the power source voltageof the latch circuits L1 and L2 still remains VDDSA.

However, if, only when the bus drive voltage is lowered, the latchcircuit L1 transmits the “H” level, there is concern that thetransmission transistor Tr2 that has to be in an OFF state depending onthe bus drive voltage and a gate electric potential G2 of thetransmission transistor Tr2 will be in the ON state. As a result, theretention data in the latch circuit L2 changes from the “H” level to the“L” level. That is, the retention data in the latch circuit L2 isdamaged. This problem is the same as in the latch circuit L1.

In order to prevent this, as described in the embodiment describedabove, the gate electric potential of the transmission transistor Tr2 isalso set to be lower than the power source voltage VDDSA of the latchcircuit L2 (equivalent to LTL=Vcll in FIG. 8). This is also true for atransmission source, the latch circuit L1. That is, the gate electricpotential of the transmission transistor Tr1 is also set to be lowerthan the power source voltage VDDSA of the latch circuit L1 (equivalentto STL=Vclm in FIG. 8).

Because of this, while maintaining stability of operation of the latchcircuit, the power consumption can be reduced.

Furthermore, according to the embodiment described above, thethree-dimensional stacked layer type NAND flash memory is described asan example of the semiconductor memory device. The three-dimensionalstacked construction is not limited specifically to a predeterminedconstruction, and a construction equivalent to the construction of thecircuit illustrated in FIG. 2 may be possible. For example, aconstruction in which transistors MT0 to MT7 are stacked on top of oneanother in the direction vertical to the semiconductor substrate may bepossible, or a construction in which a series connection between thetransistors MT0 to MT8 is arranged in a U-shaped pattern above thesemiconductor substrate may be possible. Furthermore, the embodimentdescribed above is not limited to the three-dimensional stacked type,and may be applied to a NAND flash memory and the like in the relatedart, in which the memory cells are arranged in two dimensions inside aplane of the semiconductor substrate.

Furthermore, the memory cell array illustrated in FIG. 2 may have theconfiguration in FIG. 31. FIG. 31 is a circuit diagram of a block BLK0,and the other blocks BLK can also have the same configuration as theblock BLK0. As illustrated, word lines WL0 to WL3, a dummy word lineWLDD adjacent to the word line WL0, a back gate line BG, even-numberedselect gate lines SGD0 and SGD2, and odd-numbered select gate lines SGS1and SGS3 are drawn out to one end of a memory cell array 10. Incontrast, word lines WL4 to WL7, a dummy word line WLDS adjacent to theword line WL7, even-numbered select gate lines SGS0 and SGS2, andodd-numbered select gate lines SGD1 and SGD3 are drawn out to the otherend of the memory cell array, which is opposite to the one end. Thisconfiguration may be possible. According to the present embodiment, forexample, a row decoder that selects the word line WL may be divided intotwo row decoders and the two row decoders may be arranged in such amanner that the two row decoders face toward each other with the memorycell array 10 being interposed between them. Then, the select gate linesSGD0, SGD2, SGS1, and SGS3, the word lines WL0 to WL3, the dummy wordline WLDD and the back gate line BG may be selected by one row decoderand the select gate lines SGS0, SGS2, SGD1, and SGD3, the word lines WL4to WL7 and the dummy word line WLDS may be selected by the other rowdecoder. With the present configuration, wiring congestion of the selectgate line, word line or the like in a region between a low-seriesperipheral circuit (the row decoder or a row driver) and the memory cellarray 10 can be alleviated.

Furthermore, the electric potential of the signal in the embodimentdescribed above is strictly one example and the electric potential, ifits function can be performed, is not limited to the value describedabove. Furthermore, in the flow chart described in the embodiment,processing order may be changed whenever possible.

While certain embodiments have been described, these embodiments havebeen presented by way of example only, and are not intended to limit thescope of the inventions. Indeed, the novel embodiments described hereinmay be embodied in a variety of other forms; furthermore, variousomissions, substitutions and changes in the form of the embodimentsdescribed herein may be made without departing from the spirit of theinventions. The accompanying claims and their equivalents are intendedto cover such forms or modifications as would fall within the scope andspirit of the inventions.

What is claimed is:
 1. A semiconductor memory device comprising: amemory cell array that includes multiple memory cells that are stackedabove a semiconductor substrate; and a sense amplifier that can retaindata read from or to be written to a memory cell, the sense amplifierincluding a bus that can transmit the data, a first latch circuit thatincludes a first data retention unit and a first transistor connectingthe first data retention unit and the bus, a second latch circuit thatincludes a second data retention unit and a second transistor connectingthe second data retention unit and the bus, and a third transistor,wherein when the data is transmitted from the first latch circuit to thesecond latch circuit, the third transistor is switched on to charge thebus to an electric potential lower than a power source voltage of thefirst and second latch circuits, by applying a first voltage lower thanthe power source voltage to a gate of the third transistor, and afterprecharging the bus, second and third voltages that are lower than thepower source voltage, are applied to gates of the first and secondtransistors, respectively.
 2. The semiconductor memory device accordingto claim 1, wherein the second latch circuit precharges the bus byapplying a fourth voltage that is lower than the first voltage to a gateof the second transistor, and thereafter, the third transistor isswitched on to precharge the bus.
 3. The semiconductor memory deviceaccording to claim 2, wherein a value of the first voltage is greaterthan or equal to a value of the second voltage and greater than thevalue of the third voltage, and the value of the second voltage isgreater than or equal to the value of the third voltage.
 4. Thesemiconductor memory device according to claim 1, wherein a value of thefirst voltage is less than or equal to a value of the second voltage,and the value of the second voltage is greater than a value of the thirdvoltage.
 5. The semiconductor memory device according to claim 1,wherein the first and second transistors are each an n channel MOStransistor.
 6. The semiconductor memory device according to claim 5,wherein when the data is transmitted from the first latch circuit to thesecond latch circuit, before precharging the bus, the second dataretention unit of the second latch circuit is first reset and then setto a floating state.
 7. The semiconductor memory device according toclaim 1, wherein when the data is transmitted from the first latchcircuit to the second latch circuit, the bus is set to a high logiclevel, and the second data retention unit is set to a floating statewith the high logic level, when the first latch circuit retains a highlogic level, the first and second transistors are set to an OFF state,and when the first latch circuit retains a low logic level, the firstand second transistors are set to an ON state, and the bus isdischarged.
 8. The semiconductor memory device according to claim 1,wherein at the time of data reading, the sense amplifier causes the datathat is read from the memory cell to be retained in at least one of thefirst and second latch circuits, and at the time of data writing, thesense amplifier writes the data retained in at least one of the firstand second latch circuits to the memory cell.
 9. A semiconductor memorydevice comprising: a memory cell array that includes multiple memorycells that are stacked above a semiconductor substrate; and a senseamplifier that can retain data read from or to be written to a memorycell, the sense amplifier including a bus that can transmit the data, afirst latch circuit that includes a first data retention unit and afirst transistor connecting the first data retention unit and the bus,and a second latch circuit that includes a second data retention unitand a second transistor connecting the second data retention unit andthe bus, wherein when the data is transmitted from the first latchcircuit to the second latch circuit, the second latch circuit prechargesthe bus to an electric potential lower than a power source voltage ofthe first and second latch circuits by applying a first voltage lowerthan the power source voltage to a gate of the second transistor, andafter precharging the bus, second and third voltages that are lower thanthe power source voltage, are applied to gates of the first and secondtransistors, respectively.
 10. The semiconductor memory device accordingto claim 9, wherein a value of the first voltage is greater than orequal to a value of the second voltage and greater than a value of thethird voltage, and the value of the second voltage is greater than orequal to the value of the third voltage.
 11. The semiconductor memorydevice according to claim 9, wherein the first and second transistorsare each an n channel MOS transistor.
 12. The semiconductor memorydevice according to claim 11, wherein when the data is transmitted fromthe first latch circuit to the second latch circuit, before prechargingthe bus, the second data retention unit of the second latch circuit isfirst reset and then set to a floating state.
 13. The semiconductormemory device according to claim 9, wherein when the data is transmittedfrom the first latch circuit to the second latch circuit, the bus is setto a high logic level, and the second data retention unit is set to afloating state with the high logic level, when the first latch circuitretains a high logic level, the first and second transistors are set toan OFF state, and when the first latch circuit retains a low logiclevel, the first and second transistors are set to an ON state, and thebus is discharged.
 14. The semiconductor memory device according toclaim 9, wherein at the time of data reading, the sense amplifier causesthe data that is read from the memory cell to be retained in at leastone of the first and second latch circuits, and at the time of datawriting, the sense amplifier writes the data retained in at least one ofthe first and second latch circuits to the memory cell.
 15. Asemiconductor memory device comprising: a memory cell array thatincludes multiple memory cells that are stacked above a semiconductorsubstrate; and a sense amplifier that can retain data read from or to bewritten to a memory cell, the sense amplifier including a bus that cantransmit the data, a first latch circuit that includes a first dataretention unit and a first transistor connecting the first dataretention unit and the bus, and a second latch circuit that includes asecond data retention unit and a second transistor connecting the seconddata retention unit and the bus, wherein when the data is transmittedfrom the first latch circuit to the second latch circuit, first andsecond voltages that are lower than a power source voltage of the firstand second latch circuits are applied to gates of the first and secondtransistors, respectively, when the bus is at ground voltage.
 16. Thesemiconductor memory device according to claim 15, wherein the first andsecond transistors are each an n channel MOS transistor.
 17. Thesemiconductor memory device according to claim 15, wherein when the datais transmitted from the first latch circuit to the second latch circuit,the bus is set to a high logic level, and the second data retention unitis set to a floating state with the high logic level, when the firstlatch circuit retains a high logic level, the first and secondtransistors are set to an OFF state, and when the first latch circuitretains a low logic level, the first and second transistors are set toan ON state, and the bus is discharged.
 18. The semiconductor memorydevice according to claim 17, wherein the high logic level to which thebus is set is lower than the high logic level retained by the firstlatch circuit.
 19. The semiconductor memory device according to claim15, wherein at the time of the data reading, the sense amplifier causesthe data that is read from the memory cell to be retained in at leastone of the first and second latch circuits, and at the time of the datawriting, the sense amplifier writes the data retained in at least one ofthe first and second latch circuits to the memory cell.
 20. Thesemiconductor memory device according to claim 15, wherein the firstvoltage is greater than the second voltage.